Double acting or bi-directional reciprocating pump mechanisms are often utilized in the pumping of fairly viscous liquids such as paint because these types of pumps are resistant to fouling such as by accumulated paint residue or by the particulate constituents often contained within paint. These types of pumps are also capable of adequately pumping fairly viscous fluid mediums such as polymers for protective coatings and liquid compositions having a relatively high percentage of particulate incorporated therein.
In circumstances where high volume reciprocating pump mechanisms are employed, it may be desirable to provide the inlet of the pump mechanism with a pressurized source of fluid being pumped such as by means of an external fluid supply pump. In some circumstances where pneumatic motors are utilized to drive a reciprocating pump mechanism the application of fluid pressure to the pump supply chamber can induce seal leakage at the drive motor shaft seal and thereby cause the internal components of the drive motor to be contaminated with the fluid being pumped. It is desirable, therefore, to provide a reciprocating pump mechanism having the capability of being provided with an external pressurized fluid supply source under circumstances where such is desired for high volume pumping of a fluid medium and under circumstances where any seal leakage that might occur will not cause internal contamination of the pneumatic motor.
Most reciprocating pump mechanisms are fairly complex and therefore of relatively expensive nature. It is desirable to provide a double-acting or bi-directional pump mechanism that is of simple and low cost nature.
In circumstances where different fluids are pumped by different pumps and must be delivered according to a predetermined ratio, it has been found very difficult to set up two or more independently powered pumps and then adjust them so that a precise volumetric ratio is delivered at all times. For this reason dual or multiple pumps are typically powered by a single power source. The disadvantage of this arrangement, however, is that the power source can be subjected to severe and damaging off-center loading if the fluid supply of one of the pumps becomes depleted or becomes blocked for any reason. Off-center loads can also be caused by pumps of different displacement. It is desirable therefore, to provide a pump mechanism that efficiently provides for coupling of two or more pumps to a single prime mover without subjecting the prime mover to any possibility of off-center loading.